HIF1A and breast carcinoma: Using the BCSC signature, we systematically evaluated breast cancer cell responses to chemotherapy in the perspective of BCSCs in vitro and in vivo, elucidated the key role of polyamine anabolism in the regulation of BCSCs, and developed a novel HIF‐1 inhibitor britannin that may specifically eradicate chemotherapy‐induced BCSC enrichment (Figure 4V).